Mobile communications technology has enjoyed substantial growth over the past decade. Many cars, trucks, airplanes, boats, and other vehicles are equipped with devices that allow convenient and reliable mobile communication through a network of satellite-based or land-based transceivers. Advances in this technology have also led to widespread use of hand-held, portable mobile communications devices.
Many customers of mobile communications systems also require an accurate determination of their position, and perhaps reporting of this position to a remote location. For example, a cellular telephone in a vehicle or carried by a person offers a convenient communication link to report position information. The position information may be generated by traditional positioning systems, including a satellite-based positioning system such as the global positioning system (GPS), or a land-based positioning system, such as LORAN-C. These approaches, however, may not be suitable for particular applications that require great position accuracy.